The LHCb Experiment presented at Hadron99, Beijing, August 1999 On behalf of the LHCb Collaboration Tatsuya Nakada  CERN, Switzerland  on leave from PSI

Introduction CP violation is observed only in the neutral kaon system:  : CP violation in K-K oscillations  : CP violation in the decay-oscillation interplay  : CP violation in the decay amplitudes They are within the framework of the Standard Model: KM phase. However, 1)no “precision” test has been made… (difficult with the kaon system due to theoretical uncertainties) 2)no real understanding, on the origin of the mass matrix… (Why strong CP is small but weak CP not?) 3)Cosmology (baryon genesis) suggests that an additional source of CP violation other than the Standard Model is needed. A lot of room for new physics  B-meson systems _

The B-meson system is an ideal place to search for new physics through CP violation. 1)For some decay modes, the Standard Model predictions can be made accurately. - precision tests - 2)CP violation can be seen in many decay channels. - consistency tests - The system allows to extract the parameters for both the Standard Model and new physics, if it exists.  a simple demonstration to follow

CKM Unitarity Triangles V td V tb  + V cd V cb  + V ud V ub  = 0 V td V ud  + V ts V us  + V tb V ub  = 0     V ub   V cb  V td   V ub   V td  V ts  arg V cb = 0, arg V ub = , arg V td = , arg V ts =   

new particles Extensions to the Standard Model Supersymmetry, left-right symmetric model, leptoquark, … etc. all introduces new flavour changing neutral currents  b = 1 process: Decays through penguin  b = 2 process: Oscillations through box through tree new particles bd, s b new particles d,sb b b l or l or l

H B-B        r db ]  e  i(  db ) B d -B d oscillations _ CKM and new physics in the oscillation amplitudes _ H B-B     r sb ]  e  i(  sb ) _ B s -B s oscillations _ mdmd msms CP in B d  J/  K S CP in B s  J/  H B-B  e  i(  db ) bc dd c s BdBd J/  KSKS W _ B d B d J/  K S B d _ due to the interference A B  J/  Ks  V cb  V cs  e  i |V td  V tb | 2 |V ts  V tb | 2 CP in B d  J/  K S

CP violation in B d  J/  K S v.s. B d  J/  K S measures 2  J/  K = 2(  KM  db ) _ CP violation in B d  D  n  v.s. B d  D  n  B d  D  n  v.s. B d  D  n  measures 2(  KM  db )  KM _ _ CP violation in B s  J/   v.s. B s  J/   measures 2  J/  = 2(  KM  sb ) CP violation in B s  D s  K  v.s. B s  D s  K  B s  D s  K  v.s. B s  D s  K  measures 2(  KM  sb )  KM _ _ _ A consistency test by comparing the two  KM then combine them to improve the precision

Measured  b  u          1 |V td | =              CKM angle V td  e  i  KM   semileptonic decays are least effected by new physics   Measured   from CP violation in B d  D  n , B s  D s K

2) |V ub | and  KM   KM or (  KM,  KM ) 5)  J/  K and  KM   db 3)  KM   KM 6)  J/  and  KM   sb 7)  m s,  m d and (  KM,  KM )  r db and r sb 4) (  KM,  KM )  |V td | and |V ts | 1)  KM is determined determination of CKM parameters determination of new physics parameters Both CKM and New Physics parameter sets are fully and cleanly determined. (and many other examples)

J/  K S very high statistics for a precision D  n  small asymmetries require high statistics, low background D s Kneed B s (problem for BaBar, BELLE) particle ID at large p (problem for CDF, D0) small branching fractions <   require high statistics J/  need B s (problem for BaBar, BELLE) large statistics needed to obtain CP  /CP  Potential problems for BaBar, BELLE, CDF, D0, HERA-B

The LHCb experiment Operating at the most intensive source of B u, B d, B s and B c, i.e. LHC with -particle identification -trigger efficient for both leptonic and hadronic final states. (ATLAS and CMS: no real particle ID and only with lepton triggers)

Brazil France Germany Italy Netherlands PRC Romania Spain Switzerland Ukraine UK USA The LHCb Experiment (~450 people, ~50 institutes) Poland Russia Finland

The LHCb Collaboration(August 99) Finland:Espoo-Vantaa Inst. Tech. France: Clermont-Ferrand, CPPM Marseille, LAL Orsay Germany: Humboldt Univ. Berlin, Univ. Freiburg, Tech. Univ. Dresden, Phys. Inst. Univ. Heidelberg, IHEP Univ. Heidelberg, MPI Heidelberg, Italy: Bologna, Cagliari, Ferrara, Genoa, Milan, Univ. Rome I (La Sapienza), Univ. Rome II(Tor Vergata) Netherlands: Univ. Amsterdam, Free Univ. Amsterdam, Univ. Utrecht, FOM Poland:Cracow Inst. Nucl. Phys., Warsaw Univ. Spain: Univ. Barcelona, Univ. Santiago de Compostela Switzerland: Univ. Lausanne UK: Univ. Cambridge, Univ. Edinburgh, Univ. Glasgow, IC London, Univ. Liverpool, Univ. Oxford CERN Brazil: UFRJ China: IHEP(Beijing), Univ. Sci. and Tech.(Hefei), Nanjing Univ., Shandong Uni. Russia: INR, ITEP, Lebedev Inst., IHEP, PNPI(Gatchina) Romania: Inst. of Atomic Phys. Bucharest Ukraine: Inst. Phys. Tech. (Kharkov), Inst. Nucl. Research (Kiev) U.S.A.: Univ. Virginia, Northwestern Univ., Rice Univ.

IP 8

The LHCb Detector Vertex detector: Si r-  strip detector, single-sided, 150  m thick, analogue readout Tracking system: Outer; drift chamber with straw technology Inner; Micro Strip Gas Chamber with Gaseous Electron Multiplier, Micro Cathode Strip Chamber or Si RICH system: RICH-1; Aerogel (n = 1.03) C 4 F 10 (n = ) RICH-2; CF 4 (n = ) Photon detector; Hybrid Photon Diodes (backup solution PMT) Calorimeter system: Preshower; Single layer Pb/Si (14/10 mm) Electromagnetic; Shashilik type 25X 0, ~10% resolution Hadron; ATLAS design tile calorimeter 5.6, <80% resolution Muon system: Multi-gap Resistive Plate Chamber or Thin Gap Chamber and Cathode Pad Chamber

Physics capability of the LHCb detector is due to: -Trigger efficient for both lepton and hadron high p T hadron trigger  2 to 3 times increase in , K , D  , DK ,D s , D s K … D s  : 34k (flexible and robust) -Particle identification e/  /  /K/p , K , D  , DK , D s , D s K -Good mass resolution e.g. 11 MeV for B s  D s  17 MeV for B d      (particle ID + mass resolution  redundant background rejection) -Good decay time resolution e.g. 43 fs for B s  D s  32 fs for B s  J/ 

Trigger: Flexible:Multilevel with different ingredients Robust:Evenly spread selectivities over all the levels Efficient:High p T leptons and hadrons (Level 0) Detached decay vertices (Level 1)

L0(%)L1(%)L2(%)Total(%)  ehall B d  J/  (ee)K S + tag B d  J/  (  )K S + tag B s  D s K + tag B d  DK   B d     + tag LHCb Trigger Efficiency for reconstructed and correctly tagged events - trigger efficiencies are ~ 30% - hadron trigger is important for hadronic final states - lepton trigger is important for final states with leptons

B s  D s K  Major background: B s  D s  (No CP violation) Importance of particle identification and mass resolution

B s -B s oscillations with B s  D s  120 k reconstructed and tagged events measurements of  m s  with a significance >5: up to  ps   x s  _

The LHCb detector, a forward spectrometer with particle ID, will have a wide programme in heavy flavour physics. CP violation: B d       K ±    K S K   K  +  … B s  K +  K  K ±    K S  +  … rare and forbidden decays: B s, d     ,   e ... B c meson decays b-baryon spectroscopy etc. tree + penguin penguin only

Conclusions LHCb has been approved in September 1998,  preparing for Technical Design Reports. Construction will start the beginning of LHCb is one of the four baseline LHC experiments,  taking data from the day one. Efficient and robust trigger  the optimal luminosity   exploiting the physics potential from the day one. Locally tuneable luminosity  long physics programme. Effective trigger, particle ID, decay time and mass resolution  essential to reveal New Physics from CP violation. (not possible by the general purpose LHC experiments)

LHCb CP Sensitivities in 1 year (work still in progress) ParameterChannelsNo of events  (1 year)LHCb feature 2(  +  ) B d  + c.c.6900  |P/T| = 02  -5  PID, hadron trigger B d  + c.c.~1000in progressPID, hadron trigger 2  +  B d  D    PID, hadron trigger  B d  J/  K s   -2  B s  D s K  -13  PID, hadron trigger,  t  B d  DK   PID, hadron trigger  B s  J/   t Bs oscillations x s B s  D s  upto 75 hadron trigger,  t Rare Decays BrB s   <2   t No.B d  K   26000photon trigger